EFFECT OF EXERCISE ON ENZYMATIC-ACTIVITY IN TRACHEAL FLUID AND ON INTRAPLEURAL PRESSURE DIFFERENCE IN HORSES

Seventeen trotters, eight healthy and nine with a mild respiratory dis ease, underwent a submaximal treadmill exercise. Heart rate, breathing frequency, intrapleural pressure difference (IF difference) as well a s haematocrit and concentration of lactic acid in blood were monitored before exercise, during exercise and during recovery. The activities of beta-glucuronidase and plasmin, total proteolytic activity and tryp sin inhibitory capacity were measured from the tracheal fluid before a nd after exercise. IP difference significantly increased during exerci se and returned to normal values within 15 min in healthy horses. Diff erences in intrapleural pressure between healthy and diseased horses w ere not significant during exercise. Increase of the respiratory rate was monitored during recovery probably due to respiratory compensation of the lactic acidosis. Activities of beta-glucuronidase increased an d activities of plasmin and trypsin inhibitory capacity decreased due to exercise. Most prominent changes were seen in the decrease of plasm in activity. The total proteolytic activity in the tracheal fluid befo re exercise correlated with the V-La4 values, indicating that a mild r espiratory disease, which causes proteolysis in the respiratory tract, decreases performance capacity of the horse.